Radioactive Dating: Lesson for Kids

Instructor: Nick Rogers
Have you ever seen an ancient ruin and wondered how old it is? In this lesson, you will learn about how scientists estimate the age of things when they are not sure using predictable decay rates. We will discover what a half life is and why it is important!

Ancient Ruins and Old Bones

Are you curious how old dinosaur bones really are and how scientists figure out their age? The answer to this question lies in a simple technique called radioactive dating. Radioactive dating is a way to figure out how old something is based on the fact that all things on Earth contain certain materials that change over time. Since they know exactly how fast one type of thing changes into another, they can figure out exactly how old things are based on the tiny atoms inside of them!

You may have heard of 'radioactive materials.' They can be dangerous, but many things are only a tiny bit radioactive. There are all kinds of radioactive materials inside of you right now! Radioactive substances are just things that emit energy over time. They constantly emit small amounts of radiation, and when they do this, they decay.

Assigning an age to things like bones or manuscripts is incredibly important because it helps us understand where we have been and where we are headed. Radioactive dating is how scientists figured out that the Earth is billions of years old!

Growth and Decay

Some materials change with a predictable pace. When things disappear or grow with time, we can tell how long they have been disappearing or growing by measuring the amount of 'stuff' that is still left inside of them.

Imagine that you had a box of chocolates, and you ate one half of them every hour. After one hour, you would have half a box left. Then after another hour, you would have a quarter of the box left. After the third hour, you would eat half of that and only one eighth of the box would remain and so on.

At some point, if you counted how many of the chocolates were left, could you figure out how long they had been left out? You sure could! It is possible because of the constant decay rate, the even and steady pace at which something disappears. Scientists perform a similar calculation when they are trying to find out how old things are.

What is Half-life?

The half-life of a substance is the amount of time that it takes for half of it to decay. For our chocolates example, our half-life is one hour because that's how long it takes for exactly half of the remaining chocolates to disappear.

Some things have long half-lives and those things are good for estimating the age of very old things. Some things have short half-lives (like chocolate!) and they are useful for estimating the age of younger things. One of the most important atoms that scientists study to determine the age of living things is called Carbon-14.


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